1. Field of the Invention
The present invention relates in general to a power source circuit (i.e. power supply circuit) for use in an apparatus for recording/reproducing signal, and more particularly to the technology of improving the power consumption while ensuring the convenienceness which is required in the standby state.
2. Description of the Related Art
A conventional apparatus for recording/reproducing data includes principally the following blocks. That is, the apparatus includes: a power source circuit block for generating a D.C. regulated power source voltage (i.e. power supply voltage) from an A.C. commercial power source; a block for carrying out the record and reproduction of data; and a system control block for controlling, in response to an instruction issued from a user, each of the circuit blocks.
Now, in a relatively old apparatus, in order to implement the instruction, to supply the electric power to the apparatus, which instruction has been issued from a user, a mechanical switch, a relay circuit having physical contacts, or the like is inserted into the power source circuit. For this reason, even when the power feed cord of the apparatus is connected to a mains socket of the commercial power source, if a user issues an instruction to stop the supply of the electric power from the power source circuit to the apparatus, the supply of the electric power to the apparatus is substantially interrupted and hence the state of the apparatus proceeds to the state in which no electric power is consumed therein.
On the other hand, in a recent apparatus, there is adopted the method wherein even when the apparatus is in the state in which an instruction to stop the supply of the electric power from the power supply to the apparatus has been issued from a user, an instruction to turn ON the power supply which has been issued from a user is received in the form of the instruction signal from a remote controller, or in order to reduce the cost of the power source switching circuit as described above, a small switch is provided in the position different from that of the power source circuit and the state of the switch is detected to control an electrical switch provided within the power source circuit.
In addition, in a signal recording/reproducing apparatus having a circuit for receiving the broadcasting signal which is provided either within a recording circuit or in a stage before the recording circuit, in order to carry out the reserved picture recording or the sound recording of the broadcasting signals, a clock circuit is provided either in a system controller or in the periphery thereof to automatically control the start and the end of the recording at the reserved time.
Therefore, in the recent data recording/reproducing apparatus, even when the apparatus is in the state in which an instruction to stop the supply of the electric power from the power supply to the apparatus has been issued from a user, the electric power needs to be supplied to at least the system control block. For this reason, in the state in which the power feed cord of the apparatus is connected to a mains socket of the commercial power source, even in the state in which the instruction to stop the supply of the electric power from the power supply to the apparatus has been issued from a user, the apparatus is placed in the state of consuming the electric power (hereinafter, this state is referred to as “the standby state” for short, when applicable).
Now, one might perhaps think that since in the standby state, the electric power does not need to be supplied to the data recording/reproducing block which requires the electric power the most, the load is reduced and hence the power consumption is less. However, since the power source circuit is designed to operate stably even in the case where the load is heaviest, in the case of the light load the efficiency thereof is reduced-so that the power consumption of the power source circuit itself is not decreased so much, or the power consumption of the current circuit itself may be increased in some cases. As a result, it is conventionally difficult to sufficiently reduce the power consumption of the apparatus in the standby state.
Then in order to improve this disadvantage, in a apparatus disclosed in JP-A-9-320142, there was devised the apparatus wherein in addition to the generation of the D.C. power source voltage from the commercial power source, an electric power supplying unit is provided in the form of a battery. This apparatus is designed such that a switch is provided in a power source circuit block, and upon closing of this switch, the electric power is supplied from the battery to a part of the system control block or a part of the peripheral circuits thereof. As a result, since the power consumption in the power source circuit is removed, the power consumption of the apparatus in the standby state is improved.